Calculation of the maximum load of hot water. We calculate hot water supply

The main parameters of residential buildings are water supply, sewer system and submission electrical energy. Regardless of the number of residents (a private house or a multi-storey building), the calculation of the main networks must be carried out in accordance with certain rules, using the appropriate formulas. It does not take much time to create the correct electrical circuit, it is much harder to decide on the water supply. Of particular difficulty is the design and calculation of the feed hot water. To correctly perform all operations, you need to know not only technical side issue, but also the regulatory framework.

The most commonly chosen type of circulation networks. The principle of operation of such a system is the constant circulation of the liquid. The only drawback of the hot water circulation system is that it is too expensive. The costs are justified only when the maximum number of users for a residential building is reached.

Also, in addition to the high pricing policy, the constant circulation of water leads to significant heat losses, which entails additional costs. In the presence of a circulation system, designers try to minimize the length of the pipeline. This option allows you to create additional savings on the transportation of liquid.

What is a waiting period and how is it calculated?

The waiting period is the time interval that elapses from the time the tap is opened by the user until the hot water is supplied. Given time they try to reduce as much as possible, for this they optimize the hot water supply system, make adjustments, and if the performance is poor, they modernize it.

To set the waiting period, generally accepted norms are used. To calculate it correctly, you need to know the following:

• To reduce the waiting period, you should create high pressure water in the system. But setting too high pressure parameters can damage the pipeline.
• To reduce the waiting period, increase throughput device through which the user receives liquid.
• The waiting period increases in direct proportion to the internal diameter of the pipeline, and also if there is a circuit at a great distance from the consumer.

The correct sequence for calculating the waiting period is:

• Determining the number of consumers. After the exact figure, you should make a small margin, as there are peak hot water costs.
• Determining the characteristics of the pipeline: length, internal diameter of the pipes, as well as the material from which they are made.
• Multiplying the length of the pipeline and its internal diameter by the specific volume of water, which is measured in l / s.
• Determining the shortest and most convenient fluid path. This parameter also includes the sections of the contour located the farthest from the water tap. All volumes of water are also added.
• The amount of liquid is divided by the flow of water carried out in one second. When obtaining this parameter, the total fluid pressure in the system is also taken into account.

To achieve the most accurate results, you should correctly calculate the specific volume of the pipeline. For this, the following formula is applied:

Cs = 10 (F/100)2 3.14/4 where F is the inside diameter of the pipeline.

When determining the specific volume, you cannot use the value of both the external and nominal diameters of pipes. This will significantly reduce the accuracy of the calculations. There are tables in which the value of the specific volume is pre-calculated for certain materials (copper and steel).

Calculation of hot water consumption per day

The amount of hot water that the user needs for a day is a parameter calculated in advance. Typically, such data is taken from tables, where they are divided according to the type of room and its quadrature. European parameters should not be confused with other countries, they are strikingly different from each other.

On average, the consumption of hot water per person per day is from 25 to 50 liters. Compiling and calculating the amount of hot water per person is possible only after the status of the room or building is known.

How to calculate the pipeline

For long-term operation systems for transporting hot liquids, the calculation of the pipeline should be carried out under conditions of peak loads. This allows you to make a certain margin, which will eliminate the occurrence of malfunctions in the system with a sharp increase in pressure.

For the calculation of the pipeline, most often, ready-made diagrams and tables with relevant data are used. The material most often taken is copper or galvanized steel. You should know that important parameter calculation is the equivalent Fixture Unit. This device called a conditional element for a certain type of water folding mechanisms.

Pipeline calculation sequence:

• The calculation begins with the determination of the Fixture Unit parameter, which is mandatory for each draw point.
• The main hot water transportation network is divided into separate sections(nodes). The principle is based on the design of the heating system.
• Find the total number of Fixture Units that will be located on the various sites.
• Based on the total amount of the Fixture Unit and the type of building, find the estimated flow rate for each section of the system.
• Design flow, also referred to as throughput, is an important consideration in determining the diameter of a pipeline. The inner diameter of the pipes is determined with the condition that the final figures will not exceed the generally established limits.

When calculating the circulation network, you can use general position that each Fixture Unit has 3 l/s. A separate item is the calculation recirculation pump, which has a certain throughput. To determine this parameter, it is necessary to know the exact number of water points.

To provide the circulation network with additional savings, a thermostat is installed on the pump. The thermostat ensures that the device turns on when the temperature of the transported liquid drops. When the water temperature on the return circuit reaches a value less than the nominal value by 5 degrees, the pump turns off.

What you need to have to start calculating hot water supply

It is impossible to start calculating a hot water supply system without technical and project documentation on house. At the same time, the size of the house is not important; for a private plot, the same plan is required as for a multi-storey building.

The calculation begins with a certified architectural plan, on which correct location buildings, as well as the placement of sanitary appliances. The location of the house will help you choose the supply of the water supply system along the shortest path.

You need to know the number of people who will live in the building. It is natural that the exact number of residents cannot be found out, so it is better to calculate according to the maximum data. Such figures will allow you to calculate the correct time of peak loads.

Determine the place where the hot water supply equipment will be placed. This area, in without fail must be shown on the diagram.

Water consumption for the needs of hot water supply should be determined according to the norms of hot water consumption, taking into account the likelihood of using water taps. The load on the DHW system is determined by the maximum consumption of hot water and taken into account when choosing a heat source. Hello dear friends! We are accustomed to use every day hot water and we can hardly imagine comfortable life if you can not take a warm bath or you have to wash dishes under a tap from which a cold trickle pours. Water at desired temperature and the right amount- this is what the owner of each private house dreams of. Today we will determine the estimated consumption of water and heat for the hot water supply of our house. You must understand that at this stage it is not particularly important for us where we get this heat. Perhaps we will take it into account when choosing the power of the heat supply source and will heat water for the needs of hot water supply in the boiler. Perhaps we will heat the water in a separate electric boiler or a gas column, and perhaps it will be brought to us.

Well, if there are no technical possibilities to implement the hot water system at home, then we will go to our own or the village bath. Our parents mostly went to the city baths, and now a mobile Russian bath has called under your window. Of course, life does not stand still and the presence of a bathtub and a shower cabin in the house today is no longer a luxury, but a simple necessity. Therefore, we will provide a hot water system in the house. The amount of load on the hot water supply system at home and, ultimately, the choice of heat source power will depend on the correct calculation of hot water supply. So come to this calculation need to be very serious. Before choosing the scheme and equipment of the DHW system at home, we need to calculate the main parameter of any system - the maximum hot water consumption per hour of maximum water consumption (Q g.v max, kg / h).

Practically, with the help of a stopwatch and a measuring container, we determine the flow of hot water, l / min when filling the bath

Calculation of the hourly maximum consumption of hot water per hour of its maximum water consumption

To calculate this consumption, let's turn to the hot water consumption rates (according to chapter SNiP 2-34-76), see table 1.

Hot water consumption rates (according to the chapter SNiP 2-34-76)

Table 1

g and.s - average for heating season, l/day;

g and - the highest water consumption, l / day;

g i.h - the highest water consumption, l / h.

Dear friends, I want to warn you against one common mistake. Many developers, and even young inexperienced designers, calculate the hourly maximum flow hot water formula

G max =g and.h *U, kg/h

g i.h - hot water consumption rate, l / h, the highest water consumption, is taken according to table 1; U - the number of consumers of hot water, U = 4 people.

G max = 10 * 4 = 40 kg/h or 0.67 l/min

Q g.v max \u003d 40 * 1 * (55 - 5) \u003d 2000 kcal/h or 2.326 kW

Having calculated the water flow in this way and choosing the power of the heat source to heat this flow, you calmed down. But getting under the shower, you will be surprised to find that only 3 drops of water per second drip on your dirty and sweaty bald head. Neither washing your hands, nor rinsing the dishes, not to mention taking a bath, is out of the question. So what's the deal? And the mistake is that the maximum hourly water consumption for the day of the highest water consumption is not correctly determined. It turns out that all hot water consumption rates according to Table 1 should only be used to calculate the flow rate through individual devices and the probability of using their action. These rules are not applicable to determining costs based on the number of consumers, by multiplying the number of consumers by specific consumption! This is precisely the main mistake made by many calculators when determining the heat load on the DHW system.

If we need to determine the performance of heat generators (boilers) or heaters in the absence of hot water storage tanks for subscribers (our case), then the estimated load on the DHW system must be determined by the maximum hourly consumption of hot water (heat) per day of the highest water consumption according to the formula

Q g.v max =G max * c * (t g.sr -t x), kcal/h

G max - the maximum hourly consumption of hot water, kg / h. The maximum hourly consumption of hot water, G max, taking into account the likelihood of using water folding devices, should be determined by the formula

G max = 18 *g * K and * α h * 10 3, kg / h

g - hot water consumption rate, l / with water folding devices. In our case: for a washbasin g y \u003d 0.07 l / s; for washing g m = 0.14 l / s; for a shower g d \u003d 0.1 l / s; for a bath g in \u003d 0.2 l / s. Choose greater value, that is, g \u003d g in \u003d 0.2 l / s; K and - dimensionless coefficient of use of a water-folding device for 1 hour of the highest water consumption. For a bathtub with a characteristic (highest) flow rate of hot water g x \u003d 200 l / h, given coefficient will be equal to K and = 0.28; α h is a dimensionless value determined depending on the total number N of water-folding devices and the probability of using them Р h for 1 hour of the highest water consumption. In turn, the probability of using water folding devices can be determined by the formula

R h =g and.h *U / 3600 * K and *g*N

g i.h - hot water consumption rate per hour of the highest water consumption, l / h. It is taken according to table 1, g i.h = 10l / h; N is the total number of taps installed in the house, N = 4.

R h \u003d 10 * 4 / 3600 * 0.28 * 0.2 * 4 \u003d 0.0496. At R h< 0,1 и любом N по таблице (N * Р ч = 0,198) определяем α ч = 0,44

G max \u003d 18 * 0.2 * 0.28 * 0.44 * 10 3 \u003d 444 kg / h or 7.4 l / min.

Q g.v max \u003d 444 * 1 * (55 - 5) \u003d 22200 kcal / h or 25.8 kW

No, neither the desired temperature, nor the proper flow of hot water - discomfort

As you can see, dear friends, the consumption of water and, accordingly, heat has increased by about 10 times. In addition, the heat consumption for hot water supply (25.8 kW) is 2 times more than the total heat consumption for heating and ventilation of the house (11.85 + 1.46 = 13.31 kW). If this data is presented to the "Customer", then his hair will stand on end and he will demand that they explain to him - what's the matter? So let's help him. Tables 2 and 3 below will help us with this. Now let's turn to table 2 and calculate the hourly highest flow water when loading all water consumers at the same time. Adding all the typical flow rates, we get 530 l/h. As you can see, the total typical flow rate turned out to be more than the calculated one (444l/h) by 86 l/h. And this is not surprising, since the likelihood that all water folding devices will work at the same time is very small. We have and so the value of meeting the demand for hot water from the maximum is 84%. In reality, this value is even less - about 50%. Let's try to get a real value, for this we use table 3. Do not forget that hot water consumption rates are developed for consumers at t g.av = 55 ° C, but we will find costs from the table at t g.av = 40 ° C.

The minimum total consumption of hot water, with an average water temperature equal to tg.w = 40 ° C and the simultaneous operation of all water intake devices with a security of this flow rate of 84%, will be equal to G min \u003d [ (5 * 1.5) + (20 * 5) + (30 * 6) + (120 * 10)] * 0.84 \u003d 342.3 l / h (239.6 l / h at t g.v \u003d 55 ° C)

The maximum total consumption of hot water, with an average water temperature equal to 40 ° C and the simultaneous operation of all water intake devices with a security of this flow rate of 84%, will be equal to G max \u003d [ (15 * 3) + (30 * 5) + (90 * 6 ) + (200 * 15)] * 0.84 \u003d 869.4 l / h (608.6 l / h at t g.v \u003d 55 ° C)

The average consumption at t g.w. = 55 ° C will be equal to G medium = (G min + G max) / 2 = (239.6 + 608.6) / 2 = 424.1 l / h. So we got what we were looking for - 424.1 l / h instead of 444 l / h according to the calculation.

Hot water consumption rates for water-folding devices (chapter SNiP 2-34-76)

table 2

Hot water consumption rates for various water intake devices

Table 3

Thus, when calculating hot water supply, it is imperative to take into account such nuances: the number of residents; frequency of using the bathroom, shower; the number of bathrooms where hot water is used; technical characteristics of sanitary elements (for example, the volume of a bathroom); the expected temperature of the heated water, as well as the likelihood of using water taps at the same time. In the following posts, we will take a closer look at three common hot water systems. Depending on the method of heating water, these systems, for private country house, subdivided: DHW with storage water heater(boiler); DHW with instantaneous water heater; DHW with a double-circuit boiler.

What do you think I'm doing?!!!

The obtained values ​​of water and heat consumption for the needs of hot water supply - G max \u003d 444 kg / h or 7.4 l / min and Q g.v max \u003d 22200 kcal / h or 25.8 kW we accept, with subsequent clarification, when choosing a heat source. Today we have completed the 4th point of our plan for the house - we have calculated the hourly maximum consumption of hot water for a private house. If you haven't joined yet, please join!

Sincerely, Gregory

Hot water supply is called the supply of water from elevated temperature through a centralized pipeline and internal engineering structures to private and multi-apartment buildings (including non-residential premises and premises of joint ownership). This article is devoted to the calculation of hot water supply.

In this article you will learn:

• How is the calculation of hot water.
• What formula is used to calculate the standard for hot water supply.
• How to recalculate hot water supply for general house needs.
• Why control the quality of hot water.

Calculation of the hot water supply system

The calculation of the hot water supply system is based on the calculation of heat for this type of water supply. The point is that the average temperature cold water is 10 °C, however, at the outlet this figure is much lower, which creates discomfort when using water for the consumer from the mixer (60 °C). Based on this, when calculating the temperature, it is recommended to increase it to 50 ° C.

The algorithm for calculating the average heat consumption for hot water extraction looks like this:

qm = m* t* c *∆t, kW*h,

where m is water consumption, l/h; t is the operating time, h; ∆t is the temperature difference; c is the specific heat capacity, kW x h/(l x °C).

Calculation of the standard for hot water supply

The rate of water supply (cubic meters per month for 1 person) is determined as follows:

N = Sum (Q x n) x (4.5 + 0.07 + L) x 10 where

Q - water consumption by 1 water-folding mechanism for 1 operation; n - the number of operations for using 1 water-folding device for i - 7 days; L is the number of floors in an apartment building or residential building.

Consumption rates and average water temperature per operation

The indicator of hot water supply (cubic meters per month per 1 person) is calculated as follows:

Calculation of payment for hot water supply: 2 options

Calculation No. 1 - Calculation in the residential area, a hot water consumption meter is installed.

If an individual metering device for hot water supply is installed in the apartment, the calculation of the amount of payment for hot water supply will be made according to formula No. 1, as the product of the amount of hot water consumed in the apartment according to indications individual device accounting and tariff for hot water supply established for the region and service provider:

Formula #1

P i \u003d V i p x T cr

V i p - volume(amount) consumed per billing period in a residential or non-residential hot water supply, determined according to the readings of an individual or common (apartment) meter;

T kr - tariff(price) for hot water supply, established in accordance with the legislation Russian Federation.

DHW calculation example

Based on meter readings, in January 2017. 4 m3 of hot water was used.

The cost of 1 m3 of hot water in this region, taking into account the services of an intermediary, is 90 rubles. 00 kop.

Having such data, it is possible to calculate hot water supply for this particular case:

4 x 90.00 = RUB 360.00

Calculation No. 2 - a hot water consumption meter is not installed in the living room.

For such cases, formula No. 4 is used, which takes into account data on hot water consumption rates in the region, the number of people living in the apartment and the cost of hot water supply, taking into account the region and supplier.

Formula #4

P i = n i x N j x T cr

• the number of citizens permanently and/or temporarily residing in the apartment;
• the norm established for hot water supply for the region;
• tariff set for hot water supply for the region and service provider.

DHW calculation example

If we take as a basis that three people live in the room, the rate of hot water consumption in this region is 3.5 m 3 / person, and the tariff for hot water supply is 90 rubles. 00 kop. for 1 m 3, then you can calculate the amount of payment for using hot water in a given living space as follows:

3 x 3.5 x 90.00 = 945.00 rubles.

Calculation of hot water supply for general house needs

May 06, 2011 The Government of the Russian Federation signed Decree No. 354 on a new procedure for calculating the amount of payment for utilities. According to this document, apartment residents must pay not only for hot water consumed by them at home, but also for hot water supply, which serves general house needs. These changes caused dissatisfaction among citizens and, first of all, because it was not clear what kind of surpluses water is coming speech and what it is spent on in such significant volumes.

Below is the calculation of payment for hot water supply for general house purposes.

• Calculation No. 1 - calculation of the DHW of a house on which a hot water consumption meter is not installed.

The calculation of the amount to pay for the consumed hot water for general house purposes is carried out according to the formulas No. 10, 15, which allow you to determine the amount of hot water consumed and the amount of the required payment, respectively.

Formula #10

P i one \u003d V i one x T cr

• V i od- the amount of hot water that was used for general house purposes in an apartment building and falls on a residential or non-residential premises for the billing period;
• T cr- the cost of hot water supply according to the laws of the Russian Federation.

Formula #15

V i one.5 \u003d N one x S o and x (S i / S about)

• N one- the rate of consumption of hot water supplied for the billing period and spent for general house purposes in an apartment building;
• Si- the total area of ​​residential and non-residential premises in an apartment building;
• S about- the total area of ​​all residential and non-residential premises in an apartment building;
• S oi- the total area of ​​common premises in an apartment building.

Calculation Sample

The rate of hot water consumption for general house purposes in the region is 0.3 m 3 per 1 m 2. The total area of ​​​​premises under common house management is 400 m 2. The total area of ​​all residential premises of a given apartment building equal to 4,000 m 2. The total area of ​​one apartment is 45 m2. In this region, payment for hot water is set at 90 rubles. 00 kop. for 1 m 3. Using these data, we get the following calculations:

0.3 x 400 x 45 / 4000 = 1.35 cubic meters 1.35 x 90 = 121.50 rubles

• Calculation No. 2 - calculation of the DHW of a house on which a hot water consumption meter is installed

To calculate payment DHW consumption formulas No. 10, 12 are used, which allow you to determine the amount of hot water and the amount of payment, respectively.

Formula #12

Calculation Sample

The amount of hot water that was consumed according to the common house meter is 2,000 m 3. The amount of hot water consumed in all residential premises according to indications individual counters, equal to 1 200 m 3. The amount of hot water consumed in those apartments where there are no individual meters is 500 m 3. The total area of ​​apartments in the house is 4,000 m2. The area of ​​one apartment is 45 m 2.

The cost of 1 m 3 of hot water in the region under consideration, taking into account the interests of the service provider, is 90 rubles. 00 kop.

Based on the above data, the calculation of payment for hot water supply for general house purposes is as follows:

(2,000 - 1,200 - 500) x 45/4000 = 3.375 cubic meters 3.375 x 90.00 = 303.75 rubles

Summarizing the presented examples of calculations, it should be said that in the absence of a collective meter, the volume of hot water for common house needs will be determined by the area of ​​\u200b\u200bpremises in common house ownership and the tariff for hot water supply.

It is important to know that if extra cubic meters of hot water are found, a common house meter will allow you to understand the causes of this phenomenon. If there is no such meter, then it is not possible to find the cause of the surplus and influence the amount of payment for the general house consumption of hot water.

Calculation of the load of hot water supply

The calculation of the load of hot water supply is required to be made when:

• reduction of calculated thermal loads;
• reduction of heating costs;
• coordination of changes in the composition of heat-consuming installations (change in the number heating appliances or disassembly ventilation system). This happens if the type of ventilation is changed in the room or if thermal curtain;
• the need to confirm that the new heat load and heat consumption are in line with the design norms;
• planning your own heating system;
• planning individual node heat supply;
• if necessary, correct distribution of heat load between sub-subscribers;
• connection to the common heating main of new facilities (single and/or complex structures);
• signing a new contract with a heat supplier;
• the need to specify thermal loads in non-residential premises for individual institutions;
• repayment by organizations of the cost of services by calculation (in cases where it is impossible to install a meter);
• unreasonable increase in the consumption of heat energy by the supplier or management company.

As for the rights of consumers in the field of calculating thermal energy for hot water supply, they are fixed:

• in all standard contracts concluded regarding the supply of heat and energy resources;
• in the order of the Ministry of Regional Development of the Russian Federation dated December 28, 2009 No. No. 610 “On approval of the rules for establishing and changing (revising) thermal loads”.

According to this document, the reconsideration of contractual indicators should be preceded by the creation of a technical report, which will reflect the calculation of heat loads, as well as arguments for the need to adjust or reduce the heat load on a particular object.

In addition, the order of the Ministry of Regional Development of the Russian Federation of December 28, 2009 No. No. 610 allows adjustments to be made to the calculation of heat for hot water supply, heating and ventilation in the following cases:

• during the overhaul;
• when restoring internal engineering structures aimed at reducing waste of energy resources;
• when strengthening the thermal insulation of a particular object;
• when carrying out other procedures aimed at saving energy resources.

Before starting the review of thermal loads for buildings in operation and connection to common system new objects required:

• collect all available information about the object;
• carry out an audit of the facility's power system;
• to carry out the calculation of thermal loads for hot water supply, heating and ventilation based on the results of the check;
• write a technical report;
• discuss the report with the supplier of heat and power resources;
• make adjustments to the existing one or sign a new contract with the energy supplier company.

Hydraulic calculation of hot water supply

The main goal of the hydraulic calculation of hot water supply is the calculation of the dimensions (in particular, the diameter) of the pipes through which water is supplied, and the costs of pressure. The starting value for the implementation of such calculations is considered to be the second flow rate, taking into account the value of the residual circulation:

qh, сir = qh (1 + kсir), l/s,

in this case, kсir is the residual circulation index.

To calculate this parameter, it is required to divide the second flow by the circulation inside the hot water supply system. The formula will look like this:

kсir = f(qh/qсir).

In this situation, the conditions are such that kсir ≠ 0 only in the very first parts of the pipeline, despite the fact that qh/qсir is greater than two. In all other cases, kсir will be equal to 0. The important point is that the hydraulic calculation is made before the circulation calculation. This fact implies that the specialist is forced to put forward a hypothesis about the parameters of the qh / qсir ratio (for residential buildings, qh / qсir is usually greater than 2.0) and argue it.

The calculation of the size of the cost of pressure in the water risers, united by an annular jumper into sectional nodes, is made on the basis of the estimated water flow with an index of 0.7. For the estimated flow rate in the annular sections, it is customary to take the highest second flow rate for one of the devices that is subject to maintenance as the lowest threshold.

As for the speed of movement of water in the hot water pipeline, it should not exceed three meters per second. But at the same time, it has been proven that the speed of water, exceeding one and a half meters per second, is the cause of noise.

In order to calculate the diameter of the riser when the resistance does not match, it is customary to take the estimated flow and pressure at the very base of the riser as a basis. If the resistance indicators are identical, the diameter of the extreme riser is taken as a single value.

To carry out a competent hydraulic calculation of any direction, it is required to have an idea about the basic laws of hydrodynamics (among other things, the Darcy-Weisbach equation). But you need to be prepared that each area will impose its own specifics on the implementation of the hydraulic calculation (for example, the calculation in the field of hot water supply is very typical, which eliminates the need to calculate the pressure costs separately).

There is an algorithm for calculating pressure losses in sections of the hot water supply system:

Н = i×l(1 + kl), mm,

where i - specific linear head loss, mm/m; l is the length of the section; kl is an index that takes into account pressure losses in local resistances.

Indicators i are taken from the relevant directories.

Do not forget that there are cases when hard water from the pipeline is heated for hot water supply. This situation is fraught with the appearance of growths inside the pipes (the so-called hardness salts). In this situation, a nomogram is used to calculate the index i.

• Available and required pressures in DHW systems in drawdown mode

The pressure guaranteed at the inlet and used, if necessary, to supply water for the purposes of hot water supply is called available. Another type of pressure - required, is characterized by the fact that it serves to pass the resistance of the hydraulics when water is supplied to the most remote (remotely and in height) device.

If we take as an example closed system hot water supply, then the available pressure will be the pressure of the cold water supply at the junction with the hot pipeline. And to calculate the required pressure, the following formula is used:

Nreb \u003d Npod + Nsch + Nvn + Ng + Nsv,

where Нpod - pressure loss in the supply pipelines in the drawdown mode; Нсч - pressure loss in the water meter (water meter); Hvp - pressure loss in the water heater; Hg - the difference between the geodetic indicators of the highest located device and the junction of the hot water supply system with cold water supply; Hsv - free pressure on the device ("on the spout").

For open system supply of heat resources, which involves parsing directly from the heating main, the pressure in the return water supply of the heating main at the hot water supply system connection point will be available. The calculation of the required pressure (in the absence of a water heater) will be carried out as follows:

Nreb \u003d Npod + Nsch + Ng + Hsv,

where Hg is determined from the specific place of connection to the heating main. In hot water supply systems operating on the principle of gravity under the influence of the water column in accumulating vessels, the available pressure is taken directly from the geodetic difference between the indicators of the water level in such a vessel and the device located as high as possible. The calculation of the required pressure for this situation looks like this:

Nreb \u003d Npod + Hsv

Recalculation and calculation of hot water supply

Article 542 of the Civil Code of the Russian Federation establishes that the quality of the energy resources provided must meet the criteria fixed by the law of the Russian Federation, as well as the clauses of the contract for the supply of energy resources. Article 538 of the Civil Code of the Russian Federation prescribes that the above rules be applied to relations arising from the supply of energy resources, since no other procedure is provided for by law.

The temperature of hot water in the water intake units is regulated by clause 2.4 of SanPiN 2.1.4.2496-09 " Hygiene requirements to ensuring the safety of hot water supply systems”, approved by the Decree of the Chief State Sanitary Doctor of the Russian Federation dated April 07, 2009 No. No. 20. According to this document, t at the outlet should not go beyond 60 - 75 °C. The prescriptions of SanPin must be strictly observed by those legal entities who, by occupation, are associated with the implementation and establishment of the work of the hot water supply line.

Subparagraph “B” of paragraph 17 of the Rules for Concluding Contracts for the Supply of Energy Resources indicates the importance in this area of ​​such an indicator as the quality of the resources provided, which should ensure the maintenance of common house property at the proper level. Public services must be provided to citizens in full compliance with the Rules for the provision of public services and the terms of connection apartment buildings and the common networks of engineering and technical support that unite them to centralized networks engineering and technical support (clause 20 of the Rules for Concluding Contracts for the Supply of Energy Resources).

According to clause 5, annex 1 to the Rules for the provision of public services, the quality of public services in the field of hot water supply must meet the following criteria: ensure compliance temperature regime in the water intake unit in accordance with the law of the Russian Federation on technical regulation and the provisions of SanPin.

The responsibilities of the repair and construction organization, which is responsible for the supply of water, include ensuring its quality and the desired temperature (in the range from 60 to 75 ° C), although the law of the Russian Federation does not give strict instructions on this issue. The supplier company is responsible for ensuring that the coolant reaches the citizens in the proper quality. If the water temperature indicator turns out to be less than the lower limit established by the regulations (Resolution of the AS WSO dated October 12, 2015 No. F04-24751 / 2015 in case No. A45-19993 / 2014), citizens have the right to file a claim with the court, which will oblige the defendant (company - energy supplier) to correct the violations.

Clause 5, annex 1 to the Rules for the provision of public services allows you to allow deviations from the temperature indicators established by law. So, the deviation from the accepted temperature at night from 00 h. 00 min. until 05:00 can be 5°C; in the afternoon from 05 h. 00 min. until 00 h. 00 min. - 3°C. Despite the existence of such reservations, such a provision is not considered the norm. Decision of the Supreme Court of the Russian Federation of May 31, 2013 No. No. AKPI13-394 states that such deviations are indicators of the provision of services of inadequate quality.

In order for the hot water temperature to be 60 ° C at the water intake points, it must be an order of magnitude higher at the entrance to the house. However, as already mentioned, there are no legislative regulations regarding this particular indicator, therefore, in the case of going to court, we can only talk about the fact that the repair and construction company must ensure that the water temperature at the entrance to the house is not less than 60 ° C.

When can the MKD manager apply for the recalculation of the cost of hot water

Paragraph 2 of Article 542 of the Civil Code of the Russian Federation gives citizens the right to refuse to pay for energy resources of inappropriate quality. But the supplier company is also allowed to demand from citizens in this case compensation for energy losses.

There are also legislative regulations regarding changing the procedure for paying for consumed energy resources if they were of inadequate quality or were supplied with interruptions exceeding the allowable period (subparagraph “e” of paragraph 22 of the Rules for Concluding Resource Supply Contracts). Regulate the procedure for recalculating payment Rules for the provision of utility services.

The current legislation of the Russian Federation recognizes the unconditional advantage of the system for monitoring consumed resources by installing meters in the border area between the area of ​​responsibility of the supplier company and the property of citizens. If a meter is installed on the house and there were no complaints about its operation, then the indicators of this device can be considered proof of delivery is not enough quality water. The repair and construction organization must provide evidence refuting this information, otherwise the payment for the resources expended must be recalculated (decisions of the AS UO dated January 11, 2017 No. F09-10932 / 16 in case No. A60-59444 / 2015).

This provision is also confirmed by subparagraph “B” of paragraph 111 of the Rules for the provision of public services, which determines the date and time of the start of the provision of low-quality services in accordance with the date and time fixed by the devices intended for this (for example, OPU, IPU, etc.). Moreover, the presence of a meter and its readings eliminates the procedure for confirming the fact of providing services of inadequate quality in accordance with the requirements of section X of the Rules for the provision of public services (decisions of the AS PO dated January 16, 2017 No. F06-15316 / 2016 in case No. A12-4577 / 2016).

In cases where the relevant measuring instruments not installed on the building, to confirm the fact of the provision of poor-quality services, you will need to collect a number of documents, as well as follow the procedure specified in section X of the Rules for the provision of public services:

• fix the citizen's signal to the emergency dispatch service (paragraphs 105, 106, subparagraph "b" of paragraph 111);
• agree with the citizen on the timing of verification of the information provided about the violation, notify the repair and construction organization that the service it provides will be checked if the supplier does not know the reasons for the violation (clause 108);
• check at the consumer's signal, all data obtained in the course of it must be recorded in writing according to certain form(p. 109). The audit is intended to confirm a violation in the quality of the service provided (the act of measuring the temperature at the point of analysis in the living room) and to find out its causes (the act of measuring the temperature at the entrance to the house).

Summary tables and calculations compiled unilaterally by the Criminal Code, in the absence of acts of quality control of public services, will not be accepted by the court as evidence (Resolution of the AC of the Central Organ of October 20, 2016 No. F10-2735 / 2016 in case No. A14-6593 / 2015).

Please note that the regulations do not link the establishment of the fact of supply of a low-quality resource with the fact that the utility service provider recalculates the payment for the low-quality service to the owners of the premises (Resolution of the AS ZSO dated September 19, 2016 No. F04-3939 / 2016 in case No. A03-12727 / 2015), although such a condition can be included in the resource supply agreement on the basis of an agreement between the parties, and then it must be observed.

How is hot water calculated?

Subparagraph "D" of paragraph 22 of the Rules for Concluding Contracts for the Supply of Resources says that the recalculation of the cost of a poor-quality service is carried out in accordance with the Rules for the provision of public services. This is confirmed by the Decision of the Supreme Court of the Russian Federation No. AKPI13-394, which states that if there are no additional documents that fix the procedure for recalculation, a representative of citizens living in an apartment building can claim a reduction in fees for the provision of services in violation of their quality in accordance with the requirements of SanPin. Moreover, the recalculation should be carried out in the same way as the recalculation for direct consumers (decrees of the AS of the Central Organ of February 29, 2016 No. F10-5264 / 2015 in case No. A09-1717 / 2015).

Paragraph 101 of the Rules for the provision of public services prescribes to reduce the payment for hot water supply for the billing period by the total amount of payment for the entire period of provision of low-quality services in the cases specified in the documents (see Appendices 1 and 2 of the Rules for the provision of public services).

You can determine the total cost of services with a violation of quality by multiplying the cost of the service for the entire billing period (Appendix 2 of the Rules for the provision of public services) by the ratio of the duration of the provision of low-quality services within this period to the total duration of the provision of public services for the billing period.

The following values ​​are used to calculate utility bills for hot water supply:

Pi - the amount of payment for the provided utility service for the billing period (according to Appendix 2 to the Rules for the provision of utility services);

Δ - the total amount of payment for all days of the provision of low-quality services (or the amount by which the payment should be reduced for the billing period);

t - the duration of the provision of low-quality services within one billing period.

The duration of the billing period is determined by the entire duration of the supply of energy resources in accordance with the principles of the constancy and non-stop of this process. Based on the previously described rules for calculating payment (paragraph 2 of clause 101 of the Rules for the provision of utility services), the following formula can be drawn up (assuming that the month consists of 31 days):

Δ = Рi x t / 31 days

The decrease in payment for violation of the temperature regime occurs according to the following principle: payment is reduced by 0.1% for every 3 ° C that is different from the norm (Appendix 2 to the Rules for the provision of public services) and for each hour in total throughout the entire billing period in accordance with Section IX of the Rules for the Provision of Public Services. If the temperature of hot water falls below 40 °C, then each hour of provision of the service in this way in the aggregate for the entire billing period is paid at the rate of payment for the use of cold water.

The calculations are based on the following parameters:

• the amount of payment for the relevant service for the billing period, within which failures in the organization of hot water supply were recorded (Pi1);
• the amount by which the payment for the service is reduced (in %) varies depending on fluctuations in water temperature: - 0.1% for every 3 °C;
• the duration of the provision of services with quality violations in the aggregate for the entire billing period, expressed in hours, (t1) and taking into account the rule of section IX of the already mentioned rules.

Based on all the above information, the calculation of the amount of the fee reduction is carried out according to following algorithm:

Δ = Рi1 x % x t1

The provision of paragraph 5 of Appendix 1 to the Rules for the Provision of Public Services makes it possible to apply exactly this formula, despite the prescriptions of paragraph 101 of the same Rules.

Unfortunately, in the definitions given earlier there are rough edges that cause numerous disputes and even lead to the filing of claims. Basically, the misunderstanding is related to two values, the first of which (Pi1) helps to determine the size of the reduction in pay. According to paragraph 5 of App. 1 to the Rules for the provision of public services, this payment is characterized as payment for the billing period within which temperature violations were made. However, it is worth considering in more detail the concept of the billing period and outline its scope.

Paragraph 37 of the Rules for the provision of public services speaks of the billing period as a period of time equal to one calendar month. This is confirmed by calculations in the Letter of the Ministry of Regional Development of the Russian Federation dated June 04, 2007. No. 10611-YuT/07. It is known that in private clarifications the Ministry of Construction is also of the opinion that a monthly fee should be taken into account in the calculation.

It should be noted that the definitions current Rules provision of communal services coincide in meaning with the wording that has already ceased to have its meaning in the form of performance criteria in the part under consideration (paragraph 5 of Appendix 1).

Paragraph 101 of the Rules for the provision of public services states that payment for services for a billing period equal to a month is subject to a reduction in the total amount of payment for each period for the provision of services with violations equal to one day. Thus, it is necessary to calculate the cost of providing low-quality services for 1 day.

The decision of the Supreme Court of the Russian Federation No. AKPI13-394 decides that clause 5 of Appendix 1 to the Rules for the Provision of Public Services fixes such a change in the rules for paying for public services of insufficient quality, in which it is impossible not to pay at all for the supplied water with a violation of quality. If we take the value of the payment for the month as the value of the Pi1 parameter, then even in the case of short and non-serious violations, the amount of the reduction in payment will very quickly approach this indicator, and the citizen will have to be exempted from paying for the hot water supply service for the month in question. Based on this thesis, often judges reject the claims of managers apartment buildings who provided calculations of the amount of payment, taking into account the amount of payment per month.

So, the Decree of the AC VBO of October 14, 2016 No. No. F01-3504/2016 in case No. A39-6742/2014 says that the developed system of payment for the period of poor-quality implementation of the water supply service, in which the degree of reduction in the amount of payment for the supply of hot water is considered cumulatively for the billing month, implies the possibility of not paying a spent low-quality resource, however, this is wrong. If we take the case in which the temperature of the water supplied to consumers was below the norm by 18 ° C continuously for 9 days, then according to such a calculation system, the payment for hot water per month will be 00 rubles. 00 kop. Having studied in more detail paragraph 101 of the Rules for the provision of public services, one can understand that the settlement period for the provision of a service with a violation of quality should be considered 1 day, which is confirmed by the opinion of many representatives of the panel of judges (see the decisions of the AS ZSO of October 25, 2016 No. F04-4511 / 2016 in the case No. А45-26014/2015, AS UO dated 31.03.2017 No. Ф09-1379/17 in case No. А60-14516/2016, dated 06.02.2017 No. Ф09-11636/16 in case No. А71-4808/2015).

However, in some cases, judges take the other side and recognize the legitimacy of calculating the amount of payment with a billing period of one month (see, for example, Decree of the AC ZSO of June 15, 2016 No. F04-2184 / 2016 in case No. A03-21553 / 2014).

As a possible way out, managers of an apartment building can request from the Ministry of Construction documentary evidence of an objective procedure for calculating a reduction in payment for hot water supply of inadequate quality, which can be used in court as an evidence base. However, the court has the right not to accept this document as evidence, justifying its position by the fact that the proposed documents do not have the status of normative acts.

In the case when the amount of payment for one day is taken as the basis and a meter is installed on the house, it is more correct to make calculations based on the actual amount of water used per day, which was recorded by the device. If there is no counter, then the calculations are carried out using a formula that requires dividing the total amount of the resource accounted for and delivered to the house by the number of days in the month.

Clause 5 of Appendix 1 to the Rules for the Provision of Public Services prescribes a reduction in the amount of payment for hot water by 0.1% for every 3 ° C of violation of the norm. The following criteria are also introduced here: a deviation from temperature standards 5°C at night and 3°C during the day. Thus, the exact interpretation of this regulation implies that the payment for consumed hot water should not be reduced if its temperature at night did not fall over 55 °C and below 57 °C during the day. However, if the temperature continues to fall from the already reduced levels, then for every subsequent 3°C ​​(i.e. up to 54°C), the payment will be reduced by 0.1% every hour (at 51°C - 0.2%, etc.). d.). This approach also found support among representatives of the arbitration (decisions of the AC UA dated March 31, 2017 No. F09-1379 / 17 in case No. A60-14516 / 2016, the Arbitration Court of the Far East of May 24, 2016 No. F03-976 / 2016 in case No. A24-1520 / 2015).

But Decision of the Armed Forces of the Russian Federation No. AKPI13-394 says that the establishment in paragraph 5 of Appendix 1 to the Rules for the provision of public services tolerances from the temperature regime prescribed by SanPiN 2.1.4.2496-09, in fact, means making adjustments to the sanitary and epidemiological standards governing the level of hot water quality, aimed at observing anti-epidemic measures. Such a situation is in conflict with the already mentioned legislative norms and requires the recognition of this norm as invalid in this context. Thus, we return to the fact that any deviation from the prescribed norms will be equated to violations of the quality of the service. The discussed criteria continue to apply in terms of the conditions and procedure for changing the amount of payment. Based on this, it can be concluded that a percentage of 0.1% reduction in payment for the use of hot water of inadequate quality should be charged for any violation of the temperature regime (starting from 57°C during the day and 55°C at night). In accordance with the documentary base, this approach looks more correct. He also finds support in the judiciary.

Guided by these considerations, the managers of apartment buildings should support their position with a calculation that promises great benefits, and build their line on the fact that no deviation from the temperature standards should be allowed.

There is also a nuance related to whether it is possible to calculate the exact amount of the reduction in payment if the deviation from the norm does not coincide with the “step” prescribed in the regulations. There is a point of view that recommends calculating the reduction in tenths of the payment if the temperature drops by less than 3°C. An example can be given when the water temperature during the daytime dropped to 55°C. In this case, it is possible to calculate that the percentage of the reduction in the payment for the service will be 0.167% (5/3 x 0.1%). However, the question arises as to the legitimacy of such calculations. Paragraph 5 of Appendix 1 to the Rules for the Provision of Public Services does not allow us to say that this correct solution. We remember that for every 3°C the payment decreases by 0.1%, this allows us to deduce a certain pattern.

It is this method of carrying out the calculation that is given in the Letter of the Ministry of Regional Development of the Russian Federation No. 10611-YuT / 07. A Resolution of the AS UO dated October 28, 2016 No. No. F09-9955/16 in case No. A71-5017/2015 emphasizes that the calculation of the Criminal Code is incorrect, because takes tenths of a degree into account.

Expert opinion

Why control the quality of hot water

A.N. Sokolova,

tax lawyer

The reality is that direct consumers of hot water supply (ordinary citizens, schools, kindergartens and other organizations) cannot, from a technical point of view, use the necessary equipment to monitor the quality of hot water, determine its characteristics such as color, turbidity, the amount contained in water, iron, etc. substances, etc. Also, not everyone can seek legal advice. All this implies that producers and suppliers of heat and energy resources must approach their duties with full responsibility.

A similar position is also manifested in the implementation of strict control over the quality of services provided, in the prompt elimination of identified violations and the implementation of the correct calculation of citizens for the services provided in this case. Such a result can be achieved if all parties to the process of providing the population and other subjects with heat energy direct their efforts to control the quality of the services provided. It is important that the organizations responsible for the provision of energy resources in the matter of payment for services be guided by the letter of the law and do not insist on payments for cases of quality violations. Their actions should be based on the following regulations:

• paragraph 2 of Art. 542 of the Civil Code of the Russian Federation - for organizations engaged in the supply of energy resources;
• Rules for the provision of public services - for management companies.

If these standards are not adhered to, it will be very difficult to get the supplier companies to take proper measures to eliminate possible violations in the process of supplying energy resources. Violations of the rules for the provision of services in this area and the implementation of an incorrect calculation of the population for the low-quality resources provided do not allow optimizing the state of affairs in this area in many settlements.

Throughout 2004, our organization received applications for the development of technical proposals for boiler houses for heat supply to residential and public buildings, in which the loads on hot water supply were very different (downward) from those that were previously requested for identical consumers. This was the reason for the analysis of methods for determining the loads on hot water supply (DHW), which are given in the current SNiPs, and possible errors arising from their application in practice.
E.O. SIBIRCO

Currently, the procedure for determining thermal loads on hot water supply is regulated by the normative document SNiP 2.04.01-85 * "Internal water supply and sewerage of buildings".

The method for determining the estimated flow rates of hot water (maximum second, maximum hourly and average hourly) and heat flows (heat power) during an hour at average and at maximum water consumption in accordance with Section 3 of SNiP 2.04.01–85 * is based on the calculation of the corresponding costs through water-folding devices (or groups of similar devices with subsequent averaging) and determining the probability of their simultaneous use.

All service tables with data on various specific consumption rates, etc., given in SNiP, are used only to calculate the flow through individual devices and the probability of their action. They are not applicable for determining costs based on the number of consumers, by multiplying the number of consumers by the specific consumption! This is precisely the main mistake made by many calculators when determining the heat load on hot water supply.

The presentation of the calculation methodology in the 3rd section of SNiP 2.04.01–85 * is not simple. The introduction of numerous superscript and subscript Latin indices (derived from the corresponding terms in English language) makes it even more difficult to understand the meaning of the calculation. It is not entirely clear why this was done in the Russian SNiP - after all, not everyone speaks English and easily associates the index " h"(from English hot- hot), index " c"(from English cold- cold) and " tot"(from English total- result) with the corresponding Russian concepts.

For illustration standard error, encountered in the calculations of the need for heat and fuel, I will give a simple example. It is necessary to determine the DHW load for a 45-apartment residential building with a population of 114 people. The temperature of the water in the DHW supply pipe is 55°C, the temperature of the cold water in winter period-5°C. For clarity, let's assume that each apartment has two similar water points (a sink in the kitchen and a washbasin in the bathroom).

Calculation option I is incorrect (we have repeatedly encountered this method of calculation):

According to the table "Norms of water consumption by consumers" of the mandatory Appendix 3 of SNiP 2.04.01–85 *, we determine for "Apartment-type residential buildings: with bathtubs from 1500 to 1700 mm long, equipped with showers" the consumption of hot water per inhabitant per hour of the highest water consumption is equal to q hhr, u = 10 l/h. Further, everything seems to be quite simple. The total consumption of hot water per house in the hour of greatest water consumption, based on the number of inhabitants 114 people: 10. 114 = 1140 l/h.

Then, the heat consumption in the hour of greatest water consumption will be equal to:

where U- the number of inhabitants in the house; d is the density of water, 1 kg/l; with- heat capacity of water, 1 kcal/(kg °C); t h - hot water temperature, 55°C; t c is the temperature of cold water, 5°C.

The boiler house, actually built on the basis of this calculation, clearly could not cope with the load of the hot water supply at the moments of peak hot water analysis, as evidenced by numerous complaints from the residents of this house. Where is the error here? It lies in the fact that if you carefully read section 3 of SNiP 2.04.01–85 *, it turns out that the indicator q hhr, u, given in Annex 3, is used in the calculation method only to determine the probability of operation of sanitary appliances, and the maximum hourly flow of hot water is determined quite differently.

Calculation option II - in strict accordance with the SNiP methodology:

1. Determine the probability of the device.

,

where q hhr,u = 10 l - according to Appendix 3 for this type of water consumer; U\u003d 114 people - the number of inhabitants in the house; q h0 \u003d 0.2 l / s - in accordance with paragraph 3.2 for residential and public buildings, it is allowed to take this value in the absence specifications appliances; N- the number of sanitary appliances with hot water, based on the two points of water intake accepted by us in each apartment:

N= 45 . 2 = 90 fixtures.

Thus, we get:

R= (10 x 114)/(0.2 x 90 x 3600) = 0.017.

2. Now let's determine the probability of using sanitary appliances (the ability to supply the appliance with a normalized hourly water consumption) during the estimated hour:

,
where P- the probability of operation of the device, defined in the previous paragraph, - P= 0,017; q h0 \u003d 0.2 l / s - second water flow, related to one device (also already used in the previous paragraph); q h0,hr - hourly water consumption by the device, in accordance with clause 3.6, in the absence of technical characteristics of specific devices, it is allowed to take q h0,hr = 200 l/h, then:

.

3. Since P h is less than 0.1, we apply further table. 2 of Appendix 4, according to which we determine:

at .

4. Now we can determine the maximum hourly consumption of hot water:

.

5. And finally, we determine the maximum heat load of the DHW (heat flow for the period of maximum water consumption during the hour of maximum consumption):

,

where Q ht - heat losses.

We take into account heat losses, taking them as 5% of the calculated load.

.

We got a result more than twice the result of the first calculation! As shows practical experience, this result is much closer to the actual hot water demand for a 45-apartment residential building.

It is possible to present for comparison the result of the calculation by old method, which is found in most reference books.

Option III. Calculation according to the old method. Maximum hourly heat consumption for hot water supply for residential buildings, hotels and hospitals general type by the number of consumers (in accordance with SNiP IIG.8–62) was determined as follows:

,

where k h - the coefficient of hourly uneven consumption of hot water, taken, for example, according to table. 1.14 of the handbook "Setting up and operation of water heating networks" (see table. 1); n 1 - estimated number of consumers; b - the rate of hot water consumption per 1 consumer, is taken according to the relevant tables of SNiPa IIG.8-62i for apartment-type residential buildings equipped with bathrooms from 1500 to 1700 mm long, is 110-130 l / day; 65 - hot water temperature, ° С; t x - temperature of cold water, ° С, we accept t x = 5°C.

Thus, the maximum hourly heat consumption for DHW will be equal to:

.

It is easy to see that given result almost coincides with the result obtained by the current method.

Application of the hot water consumption rate per inhabitant per hour of the highest water consumption (for example, for "Apartment-type residential buildings with bathtubs from 1500 to 1700 mm long" q hhr == 10 l/h), given in the mandatory Appendix 3 of SNiP 2.04.01–85* “Internal water supply and sewerage of buildings”, is illegal to determine the heat consumption for the needs of hot water supply by multiplying it by the number of inhabitants and the temperature difference (enthalpies) of hot and cold water. This conclusion is confirmed both by the given calculation example and by a direct indication of this in the educational literature. For example, in the textbook for universities "Heat supply" ed. A.A. Ionina (M.: Stroyizdat, 1982) on page 14 we read: “... The maximum hourly water consumption G hours max must not be mixed with the normal water consumption per hour of the highest water consumption G i.h. The latter, as a certain limit, is used to determine the probability of the action of water-folding devices and becomes equal to G hours max only with an infinitely large number of water fittings. The calculation according to the old method gives a much more accurate result, provided that the daily hot water consumption rates for the lower limit of the ranges given in the corresponding tables of the old SNiP are used, than the "simplified" calculation that many calculators perform using the current SNiP.
The data from the table of Appendix 3SNiP 2.04.01–85* must be used specifically to calculate the probability of operation of water-folding devices, as required by the methodology set out in Section 3 of this SNiP, and then determine bhr and calculate the heat consumption for the needs of hot water supply. In accordance with the note in paragraph 3.8 of SNiP 2.04.01–85 *, for auxiliary buildings industrial enterprises meaning q hr can be defined as the sum of water consumption for the use of a shower and household and drinking needs, taken according to the mandatory Appendix 3 according to the number of water consumers in the most numerous shift.

The calculation of hot water supply systems consists in determining the diameters of the supply and circulation pipelines, selecting water heaters (heat exchangers), generators and heat accumulators (if necessary), determining the required pressure at the inlet, selecting booster and circulation pumps if they are needed.

The calculation of the hot water supply system consists of the following sections:

The estimated costs of water and heat are determined and, on the basis of this, the power and dimensions of the water heaters.

The supply (distribution) network is calculated in the drawdown mode.

The hot water supply network is calculated in circulation mode; the possibilities of using natural circulation, and if necessary, parameters are determined and circulation pumps are selected.

In accordance with the individual task for the course and diploma design, the calculation of storage tanks, the coolant network can be made.

2.2.1. Determination of the estimated costs of hot water and heat. Selection of water heaters

To determine the heating surface and further selection of water heaters, hourly flow rates of hot water and heat are required, for calculating pipelines - second flow rates of hot water.

In accordance with clause 3 of SNiP 2.04.01-85, the second and hourly consumption of hot water is determined by the same formulas as for cold water supply.

The maximum second flow of hot water in any calculated section of the network is determined by the formula:

- second consumption of hot water by one device, which is determined by:

a separate device - according to mandatory Appendix 2;

various devices serving the same consumers - according to Appendix 3;

various devices serving various water consumers - according to the formula:

, (2.2)

- second consumption of hot water, l / s, by one water-folding device for each consumer group: taken according to Appendix 3;

N i is the number of water folding devices for each type of water consumer;

- the probability of operation of devices, determined for each group of water consumers;

a is the coefficient determined according to Appendix 4, depending on the total number of devices N in the network section and the probability of their action P, which is determined by the formulas:

a) with the same water consumers in buildings or structures

, (2.3)

where
- the maximum hourly consumption of hot water in 1 liter by one water consumer, is taken according to Appendix 3;

U - the number of hot water consumers in a building or structure;

N is the number of devices served by the hot water supply system;

b) with different groups of water consumers in buildings for various purposes

, (2.4)

and N i - values ​​related to each group of hot water consumers.

The maximum hourly consumption of hot water, m 3 / h, is determined by the formula:

, (2.5)

- hourly consumption of hot water by one device, which is determined by:

a) with identical consumers - according to Appendix 3;

b) for different consumers - according to the formula

, l/s (2.6)

and
- values ​​related to each type of hot water consumer;

magnitude is determined by the formula:

, (2.7)

- coefficient determined according to Appendix 4, depending on the total number of devices N in the hot water supply system and the probability of their action P.

Average hourly hot water consumption , m 3 / h, for the period (day, shift) of maximum water consumption, including, is determined by the formula:

, (2.8)

- the maximum daily consumption of hot water in 1 liter by one water consumer, is taken according to Appendix 3;

U is the number of hot water consumers.

The amount of heat (heat flow) for the period (day, shift) of maximum water consumption for the needs of hot water supply, taking into account heat losses, is determined by the formulas:

a) within the maximum hour

b) during the average hour

and - maximum and average hourly consumption of hot water in m 3 / h, determined by formulas (2.5) and (2.8);

t s is the design temperature of cold water; in the absence of data in the building, t is assumed to be + 5ºС;

Q ht - heat loss by the supply and circulation pipelines, kW, which are determined by calculation depending on the lengths of the pipeline sections, the outer diameters of the pipes, the temperature difference between hot water and the environment surrounding the pipeline and the heat transfer coefficient through the pipe walls; while taking into account the efficiency of pipe insulation. Depending on these values, heat losses are given in various reference manuals.

When calculating in course projects, heat loss Q ht by supply and circulation pipes can be taken in the amount of 0.2-0.3 of the amount of heat required to prepare hot water.

In this case, formulas (2.9) and (2.10) will take the form:

a), kW (2.11)

b) , kW (2.12)

A smaller percentage of heat loss is accepted for systems without circulation. In most civil buildings, fast sectional water heaters with variable performance are used, i.e. with adjustable heat carrier consumer. Such water heaters do not require heat storage tanks and are calculated for the maximum hourly heat flow.
.

The selection of water heaters consists in determining the heating surface of the coils according to the formula:

, m 3 (2.13)

K - heat transfer coefficient of the water heater, taken according to table 11.2; for high-speed water-to-water heaters with brass heating tubes, the value of k can be taken in the range of 1200-3000 W / m2, ºС, and the smaller one is accepted for devices with smaller section diameters;

µ - coefficient of reduction of heat transfer through the heat exchange surface due to deposits on the walls (µ=0.7);

- estimated temperature difference between the coolant and heated water; for counterflow instantaneous water heaters
º is determined by the formula:

, ºС (2.14)

Δt b and Δt m - greater and lesser temperature difference between the coolant and the heated water at the ends of the water heater.

Coolant parameters in the winter settlement period, when they work heating networks buildings, are taken in the supply pipeline 110-130 ºС and in the reverse -70, the parameters of the heated water during this period t c = 5 ºC and t c = 60 ... 70 ºC. AT summer period the heating system works only for the preparation of hot water; the parameters of the heat carrier during this period in the supply pipeline 70…80 ºC and in the return 30…40 ºC, the parameters of the heated water and t c = 10…20 ºC and and t c = 60…70 ºC.

When calculating the heating surface of a water heater, it may happen that the summer period will be decisive, when the temperature of the heat carrier is lower.

For storage water heaters, the calculation for the temperature difference is determined by the formula:

, ºC (2.15)

t n and t k - initial and final temperature of the coolant;

t h and t c - temperature of hot and cold water.

However, storage water heaters are used for industrial buildings. They take up a lot of space, in these cases they can be installed outdoors.

The heat transfer coefficient for such water heaters, according to table 11.2, is 348 W / m 2 ºC.

The required number of standard sections of water heaters is determined:

, pcs (2.16)

F is the calculated heating surface of the water heater, m 2;

f - heating surface of one section of the water heater, taken according to Appendix 8.

The pressure loss in an instantaneous water heater can be determined by the formula:

, m (2.17)

n - coefficient taking into account the overgrowth of tubes, is taken according to experimental data: in their absence, with one cleaning of the water heater per year, n = 4;

m is the coefficient of hydraulic resistance of one section of the water heater: with a section length of 4 m m=0.75, with a section length of 2 m m=0.4;

n in - the number of sections of the water heater;

v - speed of movement of heated water in the tubes of the water heater without taking into account their overgrowth.

, m/s (2.18)

q h - maximum second water flow through the water heater, m/s;

Wtotal - the total area of ​​​​the active section of the water heater tubes is determined by the number of tubes, taken according to Appendix 8 and the diameter of the tubes, taken 14 mm.